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By the end of the day this post will be three pages in the past. You'll get more views by people looking to sell if you start a want ad here... https://ratsun.net/classifieds/category/9-datsun-parts/

 

That particular transmission is a close ratio with a 3.062 first gear and an insane 0.745 over drive. Compare that to your current 4 speed first gear.

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Well as an over drive reduces engine RPMs this will also reduce power output. At some point you won't make enough power to push through the air. Remember the 0.745 was used by a much larger displacement 2.8 liter engine with much more power than say a 1.6 liter L16.

 

A 510 goes about 61 MPH at 3,500 RPMs in 4th gear. A shift into 5th reduces the RPMs by 25.5% or 892 RPMs At just over 2,600 RPMs will the L16 have enough power to maintain 60 MPH? Worse will it climb small grades or be able to drive into the wind on a windy day without down shifting?

 

Wind resistance is the thing to overcome. If it takes 10 HP to maintain 30MPH, to takes a whopping 4X or 40 HP to only just double the speed. Going fast eats HP.

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Mostly by virtue that the 510 only weighs 2,100 pounds. Small grades have less effect. Absolutely any Datsun will putt around in a zx close ratio 5 speed but the mid ratio will accelerate away faster and 5th have a more usable wider range.

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Yes, faster in 4th than 5th is because you are power limited. I think the Bonneville or maybe the BSA would go faster in 3rd than forth.  

 

Forth gear really isn't a gear, there is no gear involved when in forth. Forth is straight through the mainshaft from clutch to drive shaft and thus no side loading of the counter shaft and all those bearings. Fifth or any OD should not be used for passing or climbing hills. For that there is 4th and a lot less strain.

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If you have the money.Get one from Jasper engines and Transmissions.They are good.My 85 720 4x4 engine came from them in 2009 and my wife's transmission on a 2004 Lincoln ls 3.0 came from them in 2020.They come with a 3 year or 100,000 mile warranty,which ever comes first.But you have to have a Jasper installer to get it.They come with a Nation wide Warranty.I have over 100,000 miles on my engine.My wife has about 18,000 miles on her transmission.If something goes wrong during warranty,the installer will take it out and send it back and they will send another one.See my warranty and mileage.I now have over 385,000 miles.Cadena's installed mine.Look at the red sticker number on my engine and the one on my warranty.They are the same.Guess what motor oil I use.I better not say it cause people on here will give negative reviews.If you don't say what they use.It is no good.Same as what transmission fluid I use.Not good to say on here.FZg09M8.jpgmufqESk.jpg

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Edited by Thomas Perkins
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The 71C does not just 'drop in' and needs the driveshaft lengthened? also not sure the 71B transmission mount is in the exact same position to match the 71C, so the installer will probably balk at hearing this.

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46 minutes ago, datzenmike said:

The 71C does not just 'drop in' and needs the driveshaft lengthened? also not sure the 71B transmission mount is in the exact same position to match the 71C, so the installer will probably balk at hearing this.

I have been entertaining the  2wd D21 71C swap (completed by Madkaw and bottomwatcher) because rebuilding one of the 71B's I acquired turned out to be more involved than anticipated.(probably the reason I obtained one for free, and two were included in other deals) I tried finding someone to help but it (understandably) would cost more than paying a shop. The 71C seems a better investment choice from a do it once and never do it again standpoint.

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8 hours ago, datzenmike said:

The 71C does not just 'drop in' and needs the driveshaft lengthened? also not sure the 71B transmission mount is in the exact same position to match the 71C, so the installer will probably balk at hearing this.

Just for the record Mike the trans mount location is different. Easily solved with a small adapter.

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When I was building motors and transmissions for a living, we charged $700 for a rebuild, if your trans was in decent enough shape. We could also repair internal parts with welding and machining if required. But, most of the parts were available back then from the dealer.

 

I think I hear that Ermish charges around $1200 for a rebuild now days. At $100/hr, that's 12 hours, which is fair.

 

EDIT - ok, now you guys think I'm a greedy bastard... Justifying 12 hours for a rebuild is restoration grade work. Blueprinting and setting the stops add to the time. It can be done in just a couple hours if you want to skip the total clean/inspect phase and just throw synchros and bearings in and seal it back up.

Edited by Stoffregen Motorsports
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I think GMs 8 speeds have Americas transmission shops booked out months in advance. Personally when I buy a used transmission and can't see it work

1. I don't pay much or move on.

2. Pull the housings and inspect. If good I won. If not good I toss and move on.

With the quality of parts i have been getting I wouldn't want to run the risk of rebuilding with lower quality parts than what is in it. If everything looks good button it up, keep the gear oil topped up, change it when needed, don't abuse and enjoy.

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